The present inention relates to an ultrahigh frequency switch which is applicable up to a high frequency range above 18 GHz and provided with mechanical contacts.
Switching circuits which are operable with frequencies higher than 18 GHz (hereinafter referred to as quasimillimeter waves) may generally be classified into four types, i.e., a waveguide switch type, a coaxial switch type, a diode switch type, and a ferrite switch type.
The waveguide switch type circuit is produced by boring a part of a waveguide and mounting a rotor in the bore, the rotor being rotatable to switch the waveguide paths. This type of circuit shows significantly low insertion losses and remarkable cut-off attenuation between non-connect ports and, thereby, represents a minimum of ohmic loss on the inner surface of the waveguide to withstand passage of larger power. However, the applicable range of such a switching circuit is quite limited due to the intricate construction, large amount of switching energy, and long switcing time.
The coaxial switch type circuit includes movable center conductors in a strip line configuration which are caused into opening and closing actions toward and away from stationary contacts connected to coaxial connectors. While this type of switching circuit has a simple construction, ensures substantial cut-off attenuation, and shortens the switching time, the insertion loss undesirably increases at frequencies higher than several GHz to thereby degrade the matching condition.
The diode switch type circuit is an effective solution to the switching time problem. Nevertheless, it is unsatisfactory from the characteristics standpoint because, for example, the insertion loss is relatively high and the cut-off attenuation available therewith is not so great.
Further, the ferrite type circuit is constructed to reverse the flux direction biased on a ferrite member which is inserted in the circuit. The problem with this switching circuit is that for the flux reversal it consumes substantial energy and, in addition, the insertion loss and matching condition become poor in the ultrahigh frequency range.
With such merits and demerits of various types of switching circuits known in the art in mind, a very small switch for a waveguide which is equivalent in switching time to the previously mentioned coaxial switch type circuit and which has relatively small insertion loss even in the quasimillimeter band has been proposed as disclosed in Japanese Patent Application No. 51-146771. Using movable center conductors having a stripline configuration as switching elements, the disclosed miniature switch is capable of implementing various kinds of switch configuration such as a double-pole double-throw switch in a simple structure. However, due to the use of coaxialwaveguide transducers for a waveguide interface, the miniature switch allows the voltage standing wave ratio (VSWR) and insertion loss to increase with the circuit frequency.